Thought I'd add my feedback to the mix based on my experience revising and passing the Solutions Specialist exam.
Below were my overall revision steps:
- Read through the study guide: https://magento.com/training/free-study-guide and take particular note of the areas tested. I highlighted areas that I felt where weaknesses for me (mainly the first section on non Magento related stuff) and set out to find more info
- Read through the supplementary guides like the Demac one Miguel linked: http://www.demacmedia.com/magento-commerce/magento-certified-solution-specialist-study-guide/. I also found this pretty handy: http://thedigitalpm.com/magento-solutions-specialist-exam/, especially the 'problem scenario' questions
In regards to your comment on 'relevance' I did spot a couple of things I felt were wrong in these guides, go with your instincts on these (or check Magento to validate)
- Get local / demo copies of Magento CE and EE so you can play around in the backend to validate the queries raised / answered in the study and supplementary guides on the Magento specific sections.
Note when I took the exam 6 months ago all the questions were focused on CE 1.8 and EE 1.13 so it is imperative to reference these copies and learn their specific differences (check the study guide for the up to date info, but I doubt it's changed).
- Re-test your self on the study / supplementary guides and validate with your local / demo copies of Magento where relevant (and repeat until confident!)
Further to the above I found the greatest asset I had in passing this exam was my experience from working with Magento day to day. I feel the exam, even though multiple choice so you can to a point just learn the answers, does a great job at validating all that time spent working with Magento in the real world.
Also, don't neglect lesser known / used areas of Magento as there are questions on all facets of the system (e.g. EE payment bridge, recurring profiles)
The exam itself was not as bad as I was expecting, the pass rate is around 66% from memory and the time provided I felt was more than enough to go through all the questions multiple times (you can also flag questions to revisit later, even if answered).
On my first run through I went through all questions, answered those I knew straight away, attempted others I wasn't as confident on and flagged and skipped a few I was unsure on. I then went back again to those flagged / unanswered. Finally I reviewed the whole lot again and (rather sadly) attempted to work out if I felt I'd answered enough correctly from those I was confident on to pass!